#!/usr/bin/env python
# -*- coding:utf-8 -*-

__author__ = 'Nova'

import math


TILE_PIXEL_UNIT = 256.0
EARTH_RADIUS = 6370996.81
MCBAND = [12890594.86, 8362377.87, 5591021, 3481989.83, 1678043.12, 0]
LLBAND = [75, 60, 45, 30, 15, 0]
MC2LL = [[1.410526172116255e-8, 0.00000898305509648872, -1.9939833816331,
          200.9824383106796, -187.2403703815547, 91.6087516669843,
          -23.38765649603339, 2.57121317296198, -0.03801003308653, 17337981.2],
         [-7.435856389565537e-9, 0.000008983055097726239, -0.78625201886289,
          96.32687599759846, -1.85204757529826, -59.36935905485877,
          47.40033549296737, -16.50741931063887, 2.28786674699375, 10260144.86],
         [-3.030883460898826e-8, 0.00000898305509983578, 0.30071316287616,
          59.74293618442277, 7.357984074871, -25.38371002664745,
          13.45380521110908, -3.29883767235584, 0.32710905363475, 6856817.37],
         [-1.981981304930552e-8, 0.000008983055099779535, 0.03278182852591,
          40.31678527705744, 0.65659298677277, -4.44255534477492,
          0.85341911805263, 0.12923347998204, -0.04625736007561, 4482777.06],
         [3.09191371068437e-9, 0.000008983055096812155, 0.00006995724062,
          23.10934304144901, -0.00023663490511, -0.6321817810242,
          -0.00663494467273, 0.03430082397953, -0.00466043876332, 2555164.4],
         [2.890871144776878e-9, 0.000008983055095805407, -3.068298e-8,
          7.47137025468032, -0.00000353937994, -0.02145144861037,
          -0.00001234426596, 0.00010322952773, -0.00000323890364, 826088.5]
         ]
LL2MC = [[-0.0015702102444, 111320.7020616939, 1704480524535203,
          -10338987376042340, 26112667856603880, -35149669176653700,
          26595700718403920, -10725012454188240, 1800819912950474, 82.5],
         [0.0008277824516172526, 111320.7020463578, 647795574.6671607,
          -4082003173.641316, 10774905663.51142, -15171875531.51559,
          12053065338.62167, -5124939663.577472, 913311935.9512032, 67.5],
         [0.00337398766765, 111320.7020202162, 4481351.045890365,
          -23393751.19931662, 79682215.47186455, -115964993.2797253,
          97236711.15602145, -43661946.33752821, 8477230.501135234, 52.5],
         [0.00220636496208, 111320.7020209128, 51751.86112841131,
          3796837.749470245, 992013.7397791013, -1221952.21711287,
          1340652.697009075, -620943.6990984312, 144416.9293806241, 37.5],
         [-0.0003441963504368392, 111320.7020576856, 278.2353980772752,
          2485758.690035394, 6070.750963243378, 54821.18345352118,
          9540.606633304236, -2710.55326746645, 1405.483844121726, 22.5],
         [-0.0003218135878613132, 111320.7020701615, 0.00369383431289,
          823725.6402795718, 0.46104986909093, 2351.343141331292,
          1.58060784298199, 8.77738589078284, 0.37238884252424, 7.45]]


def convert_coord_to_mercator(lng, lat):
    ll2mc = None

    for i in range(0, len(LLBAND)):
        if lat >= LLBAND[i]:
            ll2mc = LL2MC[i]
            break

    if not ll2mc:
        for i in range(0, len(LLBAND)).reverse():
            if lat <= -LLBAND[i]:
                ll2mc = LL2MC[i]
                break

    x = ll2mc[0] + ll2mc[1]*abs(lng)
    a = abs(lat)/ll2mc[9]
    y = ll2mc[2] + ll2mc[3]*a + ll2mc[4]*pow(a, 2) + ll2mc[5]*pow(a, 3)
    y += ll2mc[6]*pow(a, 4) + ll2mc[7]*pow(a, 5) + ll2mc[8]*pow(a, 6)

    x *= (1 if lng > 0 else -1)
    y *= (1 if lat > 0 else -1)

    del ll2mc
    del a

    return x, y


def convert_mercator_to_px(x, y, z):
    x_px = math.floor(x * pow(2, z-18))
    y_px = math.floor(y * pow(2, z-18))
    return x_px, y_px


def convert_px_to_tile(x, y):
    x = int(math.floor(x/TILE_PIXEL_UNIT))
    y = int(math.floor(y/TILE_PIXEL_UNIT))
    return x, y


def get_tile(lng, lat, z):
    point = convert_coord_to_mercator(lng, lat)
    px = convert_mercator_to_px(point[0], point[1], z)
    x, y = convert_px_to_tile(px[0], px[1])

    del point
    del px

    return x, y, z

